Plasma processing systems have long been employed to process substrates to produce semiconductor devices. During substrate processing, conditions of the chamber have to be closely monitored and carefully controlled in order to create a processing environment that is conducive for creating delicate semiconductor devices. Generally speaking, manufacturers may need to create as processing environment in which the conditions are uniform in order to process a substrate.
Unfortunately, certain conditions that may exist in the processing chamber during substrate processing may cause non-uniformity. To facilitate discussion, FIG. 1 shows a simplified block diagram of a substrate processing environment 100. A substrate 106 is placed on top of an electrostatic chuck (ESC) 108 within a processing chamber 104. Power is delivered into processing chamber 104. In an example, radio frequency (RF) power 110 may be fed into processing chamber 104 via an electrostatic chuck. Within processing chamber 104, the RF power may interact with gas, which may be delivered into processing chamber 104 via a gas delivery system 102, to produce plasma 114, which may interact with substrate 106 to produce etched semiconductor products.
Ideally, the conditions within processing chamber 104, especially across substrate 106, are uniform in order to provide a uniform processing environment for processing substrate 106. However, due to the design of processing chamber 104, the conditions within the processing chamber are usually non-uniform. In an example, the radial flow of gas may cause non-uniform distribution of gas throughout the processing chamber. In another example, the gas exhaust may be non-uniformly pumped out of processing chamber 106 because a pump 112 is usually located away from the center of the substrate. Accordingly, the gas exhaust is being pumped out and downward from the center to the edge of the substrate. As a result, the gas may be non-uniformly distributed across the surface of the substrate. In an example, the gas may be less dense toward the edge of the substrate.
One method that has been employed to create a more uniform processing environment may be performed using a transformer coupled plasma (TCP) source. FIG. 2 shows a simple block diagram of a processing environment 200 utilizing a TCP source. Usually, a TCP source produces an inductive environment. Thus, instead of electrodes, set of antenna 202 may be employed to deliver power to the processing environment.
Within TCP source, plasma 206 may be generated with a doughnut shape to form a toroidal processing region. The toroidal processing region results in a radial diffusion profile over a substrate 208. However, even with a radial diffusion profile, the conditions may not be quite uniform. A larger toroidal processing region may produce a more uniform processing environment; however, a larger toroidal processing region may require the chamber to be significantly larger and the dielectric window to be larger. Accordingly, the cost associated with such an arrangement may not be financially feasible and the engineering may be significantly more difficult.